Tributes have been paid to PC David Rathband after the policeman, who was shot and blinded by Raoul Moat 18 months ago, was found dead at his home in Northumberland.

Rathband, a 44-year-old father of two, is thought to have taken his own life. A Northumbria police spokesman said no one was being sought in connection with the death.

The spokesman said officers were called to Rathband's home, in the town of Blyth, at 7pm on Wednesday following "concerns for his welfare". He was declared dead at the scene.

David Cameron described Rathband as "an extraordinarily brave man", adding: "After his horrific injuries he did an enormous amount for charities and for other injured police officers, and for families who had lost police officers in the line of duty."

The home secretary, Theresa May, said: "I had the privilege of meeting PC David Rathband. He was a brave and fine policeman. My thoughts are with his family."

Sue Sim, the chief constable of Northumbria police, said she was deeply saddened by Rathband's death, adding that he was a dedicated officer who had shown "outstanding bravery in what was a terrifying situation".

Moat, a former bouncer, became the subject of a huge manhunt after evading capture for a week before shooting himself dead after a standoff with police in the market town of Rothbury, Northumberland.

On 3 July 2010, he had shot and injured his former partner Samantha Stobbart, 22, and killed her new boyfriend, 29-year-old Chris Brown.

The following day – after having said he was "hunting for officers" – Moat crept up on Rathband as he sat in his marked police car at a roundabout above the A1 and shot him in the face and shoulder.

Rathband, who saved his life by pretending to be dead, was rushed to Newcastle general hospital and underwent surgery but lost the sight in both eyes and was left with more than 200 shotgun pellets lodged in his skull.

The officer, who joined Northumbria police in 2000, later announced that he was suing the force, claiming he had been left "a sitting duck" after Moat declared war on the police.

After the attack, he launched his own charity, the Blue Lamp Foundation, which aims to help emergency service personnel injured in the line of duty.

Rathband was widely praised for the immense courage he showed in the aftermath of the attack, but last year it became apparent that he was finding it very difficult to accept what had happened to him.

In November, he announced on Twitter that he and his wife, Kath, were separating permanently. Two months earlier, just before the start of the inquest into Moat's death, he had issued a statement saying he was to "live separately from his wife and family".

But that statement stressed the move was "purely for David's rehabilitation" and was intended to help him to continue to support his family.

It said the move had nothing to do with his arrest on suspicion of assault and stressed that "David and Kath are very much still a married couple who love each other".

Rathband was arrested in August after officers were called to an incident at his then home in Cramlington, Northumberland. He was understood to have been released shortly after police arrived.

In December, he told how he hoped to take part in trials of a revolutionary machine that could restore his eyesight by allowing him to "see" using 400 electrodes on his tongue.

The BrainPort technology, which was designed in the US, can enable blind people to visualise objects and shapes.

In a statement published on its website, the Blue Lamp Foundation said that while Rathband had "struggled to come to terms with his horrific injuries and the traumatic effect they had on him and his family and friends", his legacy would live on in the charity he established.

"The foundation was started by David to help emergency services personnel injured in the line of duty as the result of a criminal act," it said.

"It was David's wish that those who found themselves in a similar position to him could receive the support that wasn't available to him at the time." One of those leaving flowers at the officer's home on Thursday said Rathband had been Moat's last victim.

Paul Garner, who completed a sponsored walk with the policeman at the launch of the Blue Lamp Foundation, said Rathband died wanting answers as to why he was targeted by the gunman.

Placing his bouquet close to the front door of the house, Garner said: "David was one of the bravest men I have ever met.

"He was full of kindness and dignity despite what had happened to him. He kept on keeping on as long as he could but it all became too much to take. Now Raoul Moat has killed him too."

Sir Hugh Orde, the head of the Association of Chief Police Officers, said: "The death of PC David Rathband is deeply sad news for the service. He was an officer who personified the values of British policing, showing the utmost bravery when faced with danger in the line of duty. Following his ordeal, PC Rathband's courage and passion to help others through his charitable work inspired many. The thoughts of the whole police family will be with his colleagues and family at this difficult time."

The former Scotland Yard commander John O'Connor said the consequences of Rathband's injuries had been "too much for him to live with".

"No amount of counselling or compensation can give you back what you've lost, and that's the bottom line of it," he told ITV's Daybreak. "If you can't live with the consequences of the injuries you've received then, you know, this is a way out for a lot of people.

"It's dreadfully sad. There's nothing that could be done, in my view. You get all the counselling, all the help that's available, all the back-up, but the reality is you've got to live with it and if you can't, that's what happens."

He said Rathband, who came under the media spotlight following the roundabout attack, had chosen to publicise his ordeal to help other wounded officers.

"The reality was, that was his choice and that was how he felt he could deal with the injuries he received," he said.

But he added: "He's a man that suffered these appalling injuries and at the end of the day, the consequences were too much for him to live with – he couldn't bear the consequences.

"We move on, but the victims stay with their injuries and their trauma for ever."